KeywordsLeft Hemisphere Language Acquisition Vocal Tract Hemisphere Lateralization Bilingual Individual
Speaking two language, with varying degrees of proficiency.
Language is the means by which a message is communicated. Language can be spoken, heard, written, and/or read. Language consists of phonology (rules governing how sounds are formed in words), morphology (units of meaning), semantics (vocabulary and rules governing word combinations), syntax (formation of sentences), and pragmatics (how language is used in interaction and the intent or meaning of messages). This entry will address issues of monolingualism and bilingualism with regard to the evolution of language. The foremost difference is that a monolingual has fluency in one language, while bilinguals speak two languages, with varying degrees of proficiency, i.e., perfect ability is not required. Bilinguals speak their languages at the levels that are needed, not always with proficiency.
According to Chomsky (1965), most individuals are born with the capacity for learning and speaking their “native” language, or the predominant language used within their community. The nativist perspective stated that the ability to learn grammar and language is “hardwired” into everyone’s brain. Language develops without being formally taught; all human beings share a common set of cognitive abilities such that cultural variabilities are negligible. Pinker and Bloom (1990) suggest that language is attributable to human biology, rather than culture: “like echolocation in bats or stereopsis in monkeys, not like writing or the wheel.” However, individuals who are raised in feral conditions or severe neglect with little to no exposure to language early in life demonstrate very limited language acquisition (Fromkin et al. 1974); therefore, it seems that language is a combination of nativist and exposure factors.
Darwin’s theory of natural selection explains how an organism’s possession of heritable traits allows them the ability to adapt, more readily survive, and reproduce. Language is adaptive because it allows for communication among the group, cooperation, and social currency (Hagen 2008). However, Whorf (1956) believed that differences in language, grammars, and how the languages are used in different cultures affect the manner and way in which the speaker perceives the world and their environment. The products of the mind are a function of the social communities where individuals interact with each other. Thus, it is important to consider sociocultural influences on how the brain functions.
This entry will identify (a) historical influences on the acquisition of language, such as evolution of physiological improvements that promoted language, (b) cultural pressures that promote monolingualism and bilingualism among different social groups, and (c) the adaptive function of bilingualism while promoting the view that speaking more than one language produces differences in how the brain is functionally organized.
Physiological Adaptations Promoting the Evolution of Language
Numerous hominid fossils allow us to draw inferences as to how speech and language originated. The examination of prehistoric fossils demonstrates that the human species has undergone extreme and detailed physical mutations in the brain, cranium, pharynx, laryngeal, and supralaryngeal vocal tract physiology (SVT; Hagen 2008). The discovery of findings such as the bipedal female adult hominid from 3.2 million BCE, Australopithecus afarensis, and even older (4.0–4.2 million BCE) hominid species, Australopithecus anamensis and A. ramidus (4.4 billion BCE), has allowed researchers to examine vocal change physiology across time. Hagen (2008) found that A. ramidus displayed a mixture of hominid and ape features, and, even though australopithecines walked upright like humans, they had chimp-like skull shapes and characteristics, which would suggest that they may have not been any more cognitive and linguistically developed than other nonhuman primates. For instance, the chimpanzee (our closest genetic relative) is not capable of speech and vocal capabilities as humans are. They are physically unable to form vowels or consonants due to variances in their vocal tracts (Hagen 2008). If ancient hominid ancestors were nonlinguistic, yet biologically similar to modern humans, what happened between the hominid species and current Homo sapiens that allowed the genetic makeup to foster speech and language? As cited in Hagen (2008), Lieberman (2006) posits that this transition seems to be related to cranial capacity. There was a hefty increase in size of the cranium for early australopithecines, from 400 cc (3 million BCE) to 800 cc (2 million BCE) for Homo habilis and 1000 cc for Homo erectus (1.5 million BCE) and then finally 1400 cc for modern Homo sapiens (as cited by Hagen 2008). Another physiological change noted would be the development in the flexion (bending) of the base of the skull. This is thought to not only permit a longer pharynx (i.e., the throat) but also constitutes a lower positioning of the larynx (below the epiglottis, responsible for phonation, articulation, and speech) in the throat (Hagen 2008). Skull fossils including the larynx from those of the Homo ergaster (1.8 million BCE; same species as Homo erectus) were found to have limited elastic capacity compared to more recent species such as found by Tattersall (1995) Homo heidelbergensis (1 million BCE; as cited by Hagen (2008). The resulting lower position of the larynx assisted in the production and evolution of speech and, consequently, spoken language; however, this adaptation also came with difficulties. Lieberman (1998) pointed out this lower location of our larynx makes it much more likely that humans will choke on food; humans are the only mammals that cannot breathe and swallow at the same time (as cited by Hagen 2008). Dean et al. (2001) found this alteration in turn led the human supralaryngeal vocal tract to require a smaller jaw, lowering our potential for nutrient processing and resulting in less efficient mastication as our nonlinguistic predecessors, who used their jaws primarily for food crushing (as cited by Hagen 2008). However, the evolutionary adoption of one trait for a purpose other than what natural selection had intended results in transforming our vocal tract from one of an eating to a resonating and sound-producing chamber capable of speech. It is still unknown whether prehistoric hominid beings possessed language capabilities. Bickerton (1990) suggested that the Homo erectus was in fact capable of a simpler form of language: deemed protolanguage or essentially language without syntax. The Homo habilis skull suggests hemispheric specializations, suggesting some language abilities were present in the Homo erectus (as cited by Hagen 2008). In the following section, we will consider how some communities developed predominantly monolingual or bilingual language usage.
Geographical Pressures Leading to Either Monolingualism or Bilingualism
Homo sapiens began migrating to Eurasia from Africa around 120,000 BCE and most likely possessed full linguistic capabilities. The population of humans at this time was much fewer in number, estimated at no more than one tenth of one percent of our current population (Gamble 1993). However, when these social groups started increasing in number, maintaining administrative infrastructure became problematic, and consequently the groups began to splinter and disperse. This likely led to geographical separation among the groups, ultimately resulting in loss of contact. Their languages drifted, and groups formed their own dialects and eventually their own languages. The social structure of nomadic hunter-gatherers would have facilitated an engagement with other groups, and mastering languages from other groups is a critical evolutionary adaptation. This multiple language adaptability would have promoted the maintenance of social bonds among various cultures and prevention of conflicts. As Hagen (2008) specified, the primary language is used to resolve intra-cultural conflicts (or conflicts within the same social community), and second languages are utilized to resolve intercultural conflicts (or conflicts across social communities). The diversity of languages that emerged was in an effort to found and preserve cultural differences that would provide an improvement of survival. Not only would the acquisition of another language demonstrate a magnitude of social respect, but it would also help maintain intercultural affairs (such as bonds, trade, etc.) as well as a way to avoid hostility (Hagen 2008).
From a historical perspective, bilingualism has gone through many recurrent trends and extinction. A potential reason for early ancestors not learning more than one language might have resulted from population “bottlenecks” that the world was experiencing. For example, the massive eruption of a volcano in Sumatra around 75,000 BCE (Lake Toba eruption) resulted in a population drop so detrimental that only a few thousand humans were spared. Having such a small population, and paired with a nomadic lifestyle, more than one language would not have been a necessary skill to acquire (Hagen 2008).
The standard for most children to become fully fluent in a language usually requires about 2–3 years of exposure and use for conversation. Since these nomadic individuals could not contribute to this type of (linguistic and geographic) consistency, the need to learn multiple languages did not seem to be of benefit. The ebb and flow of monolingualism and bilingualism over time may have resulted from dispersion of hunter-gatherers (i.e., promoting monolingualism) and consequently at later times the forming of communities and cities (promoting bilingualism).
Sociocultural Pressures Leading to Either Monolingualism or Bilingualism
The cooperative disposition of the egalitarian communities would facilitate the need for communication. As Jacques-Rousseau alluded to in The Social Contract, the egalitarian sense of equal freedom is something we are born with, and people only deviate from this for the sake of utility (Rousseau and Gourevitch 1997). Learning another language would promote mutual respect in addition to fostering fellowship, trade, and resolution of intergroup conflicts (Hagen 2008). Contrary to this idea of cooperation, the English philosopher, Hobbes, believed that individuals are inherently violent, and morality does not exist. In Shermer’s (2004) book The Science of Good and Evil, he touched on Jane Goodall’s evidence of this primitive and aggressive behavior when observing our distant ancestors, the Pan troglodytes (chimpanzee), in Tanzania (as cited by Hagen 2008). Even though both Rousseau and Hobbes describe common behavior in response to varying predicaments, survival of the species favors the Rousseau dynamic. The species is much more likely to survive and flourish when there is cooperation and concern for others present.
Alternatively, bilingualism has been extinguished through cultural perceptions not tied to geographical limitations. Foreign languages have never been extinguished in any other country as quickly as in the United States. The concept of speaking one language is much more prevalent in the West, whereas most of the world’s population is bilingual. From the colonial days to the mid-twentieth century, the essence of “one nation, one language” was the thought process, even suggesting that this mentality would facilitate a sort of linguistic perfection. Americans during this time believed that immigrants coming to the United States should speak only English; the dedication to monolingualism was seen to be representative of faithfulness, harmony, and democracy among the country. Nebraska, for example, has had laws (from 1919) banning teaching of any foreign languages below ninth grade. The state of Nebraska organized a campaign in its honor known as “Good English” and even had students quote language loyalty oaths. Some individuals posit that the mentality behind this type of action was related to the common misconception that bilingualism created mental confusion and damaged immigrant children’s ability to adapt to their new surroundings.
This perspective continued on as recently as the early twentieth century. The prevalent belief was that bilingualism does not benefit individuals, but instead hinders cognitive abilities of dual-language persons, especially in children. A common misconception is that genetic differences between races prohibited immigrants to learn English, which in turn was perceived as a lower intelligence level. The other explanation was that since the child spoke in their foreign language at home, and English at school, perhaps the dual vocabulary and lexicon impeded each other. Peal and Lambert (1962) shed light on this issue and found that, when controlling for social class, bilingualism actually produced higher results on a number of intelligence tests. They not only found that two vocabularies actually improved comprehension for bilingual individuals but also enhanced multiple higher cognitive abilities including concept formation (Liedtke and Nelson 1968), metalinguistic awareness (Cummins 1978), and code-switching, which demonstrates intellectual advantages (Hughes et al. 2006). The next section explores neuroanatomical differences and cognitive benefits of bilingualism as a positive adaptation and a mechanism to improve brain function and plasticity.
Hemispheric Lateralization and Specialization in Language Processing
The first identification of the brain being acknowledged as the center of language was indicated in the Edwin Smith papyrus, in approximately 3500 BC (Ahlsén 2006). The specific neuroanatomical location was later discovered by Broca upon autopsy of two of his patients; both had suffered severe language-speaking deficits, yet retained relatively good comprehension abilities with impaired speaking abilities. Both had injuries to the inferolateral frontal cortex (Broca 1861). He surmised that linguistic symptoms were caused by these left hemisphere lesions, and therefore language was located, and lateralized, in the left hemisphere. Later, Carl Wernicke (1874) identified the temporal-parietal regions as the processing center of language comprehension, an area separate from spoken language. He also proposed the idea of language functions localized in the gyri (brain convolutions). Other evidence has supported this belief of language-related initiation, specifically in areas such as the gyri (lingual and fusiform), middle prefrontal areas (such as the dorsolateral prefrontal cortex), the insula, and even middle and inferior temporal gyri and temporal pole (Obler and Gjerlow 1999). Processing language, as well as the language acquisition center, is predominantly associated with the language centers located in the left hemisphere of the primary and secondary auditory cortices, more specifically the perisylvian region of the left hemisphere (Hagen 2008). The right hemisphere has been labeled the nondominant hemisphere as noted by studies indicating that significant speech, language, and reading disabilities occur when lesions are located in the left hemisphere (Ardila and Ostrosky-Solis 1984). Abutalebi et al. (2001) suggested that activation of the right hemisphere occurs in mirror regions during language tasks. Although evidence for right hemisphere function of certain linguistic abilities has been found, 97% of nondisabled right-handed people and 70% of nondisabled left-handed people have left hemisphere lateralization (Obler and Gjerlow 1999). This presumption of left hemisphere lateralization was identified in Lenneberg’s 1964 study of language loss in young children with left hemisphere brain injuries. Lenneberg et al. (1967) later proposed evidence to support a critical period hypothesis (CPH), a theory in which language acquisition and linguistic ability are tied to biological age, cutoffs, and language fossilization (i.e., language growth stopping at a certain age). This hypothesis is explored in the context of early versus late second language acquisition. Lenneberg et al. (1967) postulated the critical period consisted of 2 years to about 14 years of age. Patkowski (1980) examined the concept of a sensitive period, which references a preferred age for second language acquisition and windows of opportunity for best acquiring language. He investigated the idea of native-like acquisition of syntax in a nonnative language and hypothesized that it would be more difficult to achieve native-like fluency unless the individual began to acquire the second language before the age of 15. He surmised that this native proficiency is not necessarily dependent on the age of puberty, but rather the utilization of sociolinguistic conditions prior to puberty, such as exposure, practice time, etc. Consequently, it is possible to acquire a second language after this “critical period”; however, it is somewhat harder to reach native-like fluency in the second acquired language after the sensitive period (Patkowski 1980).
Neural plasticity may be an underlying mechanism promoting greater fluency with earlier second language (L2) acquisition. Plasticity also mediates recovery of language functioning such that when second language acquisition occurs before 7 years of age, language is more resilient to disease and injury compared to those who learn after this sensitive period (Fabbro 2001). Hagen (2008) states that almost all childhood aphasia studies have shown 75–100% recovery rates. In addition, Paradis (1977) found that after a stroke there were different degrees of rehabilitation in each language for bilinguals. Hernandez et al. (2000) stated that there have been no clear rules in relation to recovery patterns; however, they found that factors such as first language learned, language use before aphasia, and language dominance all played into varying degrees of language recovery. While these studies demonstrate the influence of age of acquisition and plasticity on first language (L1), and L2, language localization is also an important element to consider.
Brain organization and language localization for monolingual and bilingual individuals is not a straightforward proposition. The left hemisphere has been known for most expressive and receptive language functions. However, brain localization for bilingual individuals may differ for their L1 and L2. For example, Gomez-Tortosa et al. (1996) presented a case study of a bilingual patient with selective impairment in L1 (but not L2) after surgery to remove a lesion in her left perisylvian area of the brain. Alternatively, L2 could be localized in the right hemisphere. Dehaene et al. (1997) identified, using fMRI, that although L1 seems to be mediated by a similar brain network in individuals they assessed, the L2 produced activation in left and right temporal and frontal areas, occasionally restricted only to the right hemisphere (namely, the right superior temporal gyrus and superior temporal sulcus). Perani et al. (1996) used positron emission tomography (PET scans) and revealed that when late second language learners listened to L1 (i.e., their native languages), it activated brain areas that are not apparent in L2 (i.e., the second language) for late second language acquisition learners. These brain areas included both left and right temporal lobes, left inferior parietal lobe, and left inferior frontal gyrus. These findings demonstrate variation in patterns of localization and lateralization of function. A meta-analysis of 66 studies suggests that age of acquisition was a strong predictor of lateralization (Hull and Vaid 2007). When L2 learning occurred before the age of 6, bilateral organization was common, whereas after the age of 6, both languages were predominantly left lateralized. Hull and Vaid (2007) suggest that when infants are learning two languages simultaneously, pragmatic cues are needed to differentiate between the two languages, which underlies the right hemisphere involvement. Alternatively, they suggest that the extensive requirement for learning two languages promoted involvement of both hemispheres and produced automaticity in these areas. The age of 6 is a specific time in brain development during which neural wiring and pruning take place (Huttenlocher and Dabholkar 1997, as cited by Hull and Vaid 2007). Right hemisphere involvement in language acquisition after this point may be less efficient and involves less automaticity than left hemisphere involvement. For example, recent research utilizing a timed picture-naming task provided evidence that early second language learners exhibited faster response times and speed accuracy compared to those who learned their second language later (Kohnert et al. 1998).
Both physiological adaptations and sociocultural processes favor and promote bilingual speaking in communities. Evolutionary forces across time have warranted the opportunity for our brains to evolve and be ready for the learning of language such that our vocal tracts are not only necessary for eating but evolved for speech. Although the downsides include not being able to breathe and swallow at the same time, increased likelihood of choking on food, and decreased nutrient processing (Hagen 2008), the benefit of developing such complex vocalizations as symbolic language far outweighs these costs. Brown et al. (1985) postulated that the use of symbolic language allowed for complex thought and heightened the cognitive capacity of the human brain as evidenced in the increasing size of the cranium (as cited by Hagen 2008) and volume of prefrontal brain matter (Schoenemann et al. 2005). With these physiological adaptations in place, humans were poised to begin a new phase of adaptation involving complex oral linguistic communication within and across social communities. As humans began migrating to other areas and splintering due to instabilities in large community sizes, languages diverged and evolved as well. However, some communities had the opportunity to utilize second language acquisition through sociocultural interaction, whereas others were constrained by geographical isolation or cultural mores to speak only one language. For those who had geographical access to communities speaking another language, learning a second language was adaptive because it promoted development of intercultural bonds and access to resources.
Not only would speaking two languages be adaptive socioculturally but also cognitively and physiologically. A pattern emerges in the research on the areas of the brain associated with speech and language. The left hemisphere is specialized for language processing, but bilingual brain organization is dependent on factors such as age of acquisition, exposure, and practice; consequently, learning a second language is recommended before the age of six (Hull and Vaid 2007) or before one reaches puberty (Patkowski 1980) due to greater brain plasticity. Indeed, the acquisition of a second language has profound effects on the brain, leading to improvements in executive function (Bialystok 2015), task switching (Prior and MacWhinney 2010), conflict resolution (Bialystok et al. 2012), and metalinguistic awareness (Galambos and Hakuta 1988), as well as and serving as a protective factor against age-related dementia and Alzheimer’s disease (Bialystok et al. 2012). The neurological benefits of bilingualism have been found to increase gray matter volume in bilinguals, compared to monolinguals (Olulade et al. 2016).
In a world that is becoming more globalized, the benefits of bilingualism cannot be ignored. While geographic limitations may inhibit direct communication with others, communities can be easily accessed through the Internet. Exposing children to other languages early in life and fostering communication digitally as well as in person could lead to lasting positive changes in the brain and cognition, as well as promote cultural competence. Bilingualism can be adaptive since it allows individuals to have exposure to other cultures through different languages, in addition to establishing a sense of interconnectedness.
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